lightroom 6

Your post is unclear.  I assume you're looking for a link to LR6 installer for Mac?  If yes, contact the vendor who sold it to you.  

Also, older 32-bit software won't work on mac OS Catalina.   Unless you have an older supporting OS (Mojave or earlier), you will need new software. 

Lightroom Compatibility on Catalina

https://helpx.adobe.com/lightroom-classic/kb/macos-catalina-compatibility.html

Creative Cloud Photography Plan (approx $10/month for 12 months).

https://www.adobe.com/creativecloud/photography.html

For CS6 and earlier you may download ONLY if you bought direct from Adobe via download
-Log-in to your account and click this link https://account.adobe.com/products
--click Order history on the left and then the link to your order that will show on the right
--and finally click the link "Downloads and serial numbers" that will appear
--as always, write the serial number in a text file AND copy that text file and the
---download file(s) to an external drive (or two) to be sure you have what you need
-if you did not buy direct from Adobe via download you must find your original install
--if you have an Education or volume license you MUST use your original media
--the link for an Education or volume license download is not available at all
-if you bought a disc and don't have a drive you will need to buy an external USB drive
-if you bought a download from a 3rd party vendor you will need to contact that vendor